Geothermal Energy Potential in Selected Areas of Western Australia ...

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T=T0+QR, where R=z/ (average thermal conductivity between the surface and z).
Consequently the most highly prospective regions for geothermal exploration are
those that have geological units of sufficiently low conductivity (high thermal
resistance) in the cover sequence combined with high heat flow.
Heat flow is the product of temperature gradient and rock thermal conductivity. It is
therefore calculated, or modelled, from these two parameters, not directly measured.
The modelling of heat flow is a precision skill that requires a detailed understanding
of physical conditions in the borehole and the physical properties of the rocks;
including advective processes that may influence bore temperature (such as ground
water flow or borehole convection), and the temperature dependence of conductivity.
Heat flows determinations are only as accurate as the data used to generate them. It
is therefore important
that temperature and conductivity data used to calculate heat
flow represent as closely as possible the actual thermal conditions.
HDRPL’s 1D Conductive Heat Flow Modelling software accounts for the temperature
dependence of conductivity. However,
the results of 1D heat flow modelling should
be treated with caution when extrapolating data laterally over considerable distance.
HDRPL recommends a subsequent, more detailed appraisal of the Perth Basin,
incorporating the data derived from this study and utilising 3D conductive heat flow
modelling software.
4.3. Verification of Well Temperatures
Reported well temperatures measured during the drilling process are often of
unknown
quality. Even reliably reported temperature data typically underestimate the
true rock temperature because of the cooling effect of circulating drilling mud. In
order to ensure the most accurate data are used in the thermal modelling process,
statistical corrections (such as Horner Plots) can be applied to time series data
recorded during the logging process.
The Horner plot method corrects for bore hole cooling created by the drilling process
using the parameters of recorded bore hole temperature; the time since the last fluid
circulation; and the time elapsed between
the end of drilling and the cessation of fluid
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